U.S. patent number 8,431,278 [Application Number 12/701,864] was granted by the patent office on 2013-04-30 for passive water drain.
This patent grant is currently assigned to GM Global Technology Operations LLC. The grantee listed for this patent is Steven G. Goebel, William H. Pettit. Invention is credited to Steven G. Goebel, William H. Pettit.
United States Patent |
8,431,278 |
Goebel , et al. |
April 30, 2013 |
Passive water drain
Abstract
A passive water drain for removal of water from a fuel cell
system is disclosed, the drain including a main body having a
cavity formed therein, an interior element, and a hydrophilic
porous media. The passive water drain is adapted to simplify the
anode reactant recycler, eliminate the need for bypass valve
systems used to remove water from the cathode exhaust, and
eliminate the need for condensate draining systems used for
compressed air entering the cathode.
Inventors: |
Goebel; Steven G. (Victor,
NY), Pettit; William H. (Rochester, NY) |
Applicant: |
Name |
City |
State |
Country |
Type |
Goebel; Steven G.
Pettit; William H. |
Victor
Rochester |
NY
NY |
US
US |
|
|
Assignee: |
GM Global Technology Operations
LLC (Detroit, MI)
|
Family
ID: |
44316827 |
Appl.
No.: |
12/701,864 |
Filed: |
February 8, 2010 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20110195344 A1 |
Aug 11, 2011 |
|
Current U.S.
Class: |
429/414; 137/179;
429/450; 137/177; 429/415 |
Current CPC
Class: |
H01M
8/04126 (20130101); H01M 8/04149 (20130101); H01M
8/04089 (20130101); H01M 2250/20 (20130101); H01M
2008/1095 (20130101); Y02T 90/40 (20130101); Y02E
60/50 (20130101); Y10T 137/3028 (20150401); Y10T
137/4238 (20150401); Y10T 137/3021 (20150401) |
Current International
Class: |
H01M
8/04 (20060101); F16T 1/34 (20060101) |
Field of
Search: |
;429/414
;137/177,179 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Maples; John S
Attorney, Agent or Firm: Fraser Clemens Martin & Miller
LLC Miller; J. Douglas
Claims
What is claimed is:
1. A device for receiving a fluid stream comprising: a main body
having a cavity formed therein, the main body including an inlet,
an outlet, a passive water drain, and a drain conduit coupled to
the passive water drain, wherein the inlet is adapted to receive
the fluid stream and the drain conduit does not include a valve; an
interior element disposed in the cavity of the main body adapted to
increase a tortuosity of the fluid stream; and a hydrophilic porous
media disposed within the passive water drain in fluid
communication with the cavity, the hydrophilic porous media
configured to militate against transfer of the fluid stream through
the passive water drain and to allow liquid water to pass through
the passive water drain, wherein the fluid stream is exhausted from
the cavity through the outlet.
2. The device for receiving a fluid stream according to claim 1,
wherein the fluid stream includes a liquid, the liquid collecting
in the cavity thereby hydrating the hydrophilic porous media, the
liquid in excess of a saturation point of the hydrophilic porous
media exiting the cavity through the passive water drain.
3. The device for receiving a fluid stream according to claim 1,
wherein one of a thickness and an area of the hydrophilic porous
media is selected to militate against transfer of the fluid stream
through the passive water drain.
4. The device for receiving a fluid stream according to claim 1,
wherein the hydrophilic porous media is sealingly disposed in the
passive water drain.
5. The device for receiving a fluid stream according to claim 1,
wherein the hydrophilic porous media has a pore size from about 1
to about 10 microns.
6. The device for receiving a fluid stream according to claim 1,
wherein the hydrophilic porous media is one of a glass fiber mat, a
sintered metal, a bonded metal mesh, a woven cloth, and a porous
foam.
7. The device for receiving a fluid stream according to claim 1,
further comprising a strainer disposed in the inlet of the main
body.
8. The device for receiving a fluid stream according to claim 1,
further comprising a liquid retention feature disposed adjacent the
hydrophilic porous media.
9. The device for receiving a fluid stream according to claim 1,
wherein the cavity of the main body is adapted to be in fluid
communication with an anode outlet of a fuel cell system.
10. The device for receiving a fluid stream according to claim 9,
further comprising a water vapor transfer unit in fluid
communication with the cavity of the main body.
11. The device for receiving a fluid stream according to claim 10,
wherein the cavity of the main body is adapted to be in fluid
communication with one of a cathode inlet and a cathode outlet of a
fuel cell system.
12. The device for receiving a fluid stream according to claim 1,
further comprising an intercooler in fluid communication with one
of the inlet and the outlet of the main body.
13. A device for receiving a fluid stream in a fuel cell system
comprising: a main body having a cavity formed therein, the main
body including an inlet, an outlet, a passive water drain, and a
drain conduit coupled to the passive water drain, wherein the inlet
is adapted to receive the fluid stream and the drain conduit does
not include a valve; an interior element disposed in the cavity of
the main body adapted to increase a tortuosity of the fluid stream;
a hydrophilic porous media sealingly disposed in the passive water
drain in fluid communication with the cavity; and a liquid
retention feature disposed adjacent the hydrophilic porous media,
wherein the hydrophilic porous media is configured to militate
against transfer of the fluid stream through the passive water
drain and and to allow liquid water to pass through the passive
water drain, wherein the fluid stream is exhausted from the cavity
through the outlet.
14. The device for receiving a fluid stream in a fuel cell system
according to claim 13, wherein the fluid stream includes a liquid,
the liquid collecting in the cavity thereby hydrating the
hydrophilic porous media, the liquid in excess of a saturation
point of the hydrophilic porous media exiting the cavity through
the passive water drain.
15. The device for receiving a fluid stream in a fuel cell system
according to claim 13, wherein one of a thickness and an area of
the hydrophilic porous media is selected to militate against
transfer of the fluid stream through the passive water drain.
16. The device for receiving a fluid stream in a fuel cell system
according to claim 13, wherein the hydrophilic porous media has a
pore size from about 1 to about 10 microns.
17. The device for receiving a fluid stream in a fuel cell system
according to claim 13, wherein the hydrophilic porous media is one
of a glass fiber mat, a sintered metal, a bonded metal mesh, a
woven cloth, and a porous foam.
18. The device for receiving a fluid stream in a fuel cell system
according to claim 13, wherein the cavity of the main body is
adapted to be in fluid communication with at least one of an anode,
a cathode, and a water vapor transfer unit of a fuel cell
system.
19. The device for receiving a fluid stream in a fuel cell system
according to claim 13, further comprising a strainer disposed in
the inlet of the main body.
Description
FIELD OF THE INVENTION
The present invention relates to a fuel cell system and, more
particularly, to an apparatus for passive removal of water from the
fuel cell system.
BACKGROUND OF THE INVENTION
A fuel cell has been proposed as a clean, efficient, and
environmentally responsible energy source for electric vehicles and
various other applications. In particular, the fuel cell has been
identified as a potential alternative for the traditional
internal-combustion engine used in modern vehicles. One type of
fuel cell is known as a proton exchange membrane (PEM) fuel cell.
Individual fuel cells can be stacked together in series to form a
fuel cell stack. The fuel cell stack is capable of supplying a
quantity of electricity sufficient to provide power to a
vehicle.
Hydrogen is a very attractive fuel because it is clean and can be
used to efficiently produce electricity in the fuel cell. A
hydrogen fuel cell is an electro-chemical device that includes an
anode and a cathode with an electrolyte therebetween. The anode
receives hydrogen gas and the cathode receives oxygen or air. The
hydrogen gas is dissociated in the anode to generate free protons
and electrons. The protons pass through the electrolyte to the
cathode. The electrons from the anode cannot pass through the
electrolyte, and thus, are directed through a load to perform work
before being sent to the cathode. The protons react with the oxygen
and the electrons in the cathode to generate water. Not all of the
hydrogen is consumed by the stack, and some of the hydrogen is
output as an anode exhaust gas that may include water and
nitrogen.
Proton exchange membrane fuel cells (PEMFC) are a popular fuel cell
for vehicles. The PEMFC generally includes a solid
polymer-electrolyte proton-conducting membrane, such as a
perfluorosulfonic acid membrane, for example. The anode and cathode
typically include finely divided catalytic particles, usually
platinum (Pt), supported on carbon particles and mixed with an
ionomer. The catalytic mixture is deposited on opposing sides of
the membrane. The combination of the anode catalytic mixture, the
cathode catalytic mixture, and the membrane define a membrane
electrode assembly (MEA).
Several individual fuel cells are typically combined in a fuel cell
stack to generate the desired power. For the automotive fuel cell
stack mentioned above, the stack may include two hundred or more
fuel cells. The fuel cell stack typically includes fuel cell
subsystems and related devices that aid in the preconditioning and
operation of the fuel cell stack. As nonlimiting examples, the fuel
cell subsystems and related devices housed within the main body can
include end plates, fluid passages, e.g. hydrogen fuel and oxidant
(O2/air) passages, coolant pumps, recirculation pumps, drainage
valves, fans, compressors, valves, electrical connections,
reformers, humidifiers, water vapor transfer units, heat
exchangers, and related instrumentation.
Liquid water present in the fuel cell stack and the fuel cell
subsystems may prevent optimal operation of the fuel cell stack.
Liquid water may block gas flow within the fuel cell stack and the
fuel cell subsystems and may freeze when the fuel cell stack is not
operating. A portion of the anode exhaust gas may be recycled to
maintain an anode stoichiometry without the use of excess hydrogen.
When cold hydrogen is injected into a desired anode reactant
recycler in fluid communication with the anode, water vapor present
in the exhaust gas condenses and is separated from the exhaust. Ice
may prevent the operation of a combined bleed and drain valve used
to remove the water and excess nitrogen from the fuel cell stack,
increasing a startup time of the fuel cell stack. The combined
bleed and drain valve minimizes complexity and is typically located
adjacent a water collecting portion of the fuel cell subsystem the
combined bleed and drain valve is incorporated in. Alternately,
separate valves (a bleed valve and a drain valve) may be used to
perform bleed and drain functions in the fuel cell subsystem.
Excess nitrogen may be present in the anode of the fuel cell stack
and the fuel cell subsystems as a result of extended periods of
non-operation of the fuel cell stack, or as a result of bleed
through from the cathode. Nitrogen present within the fuel cell
stack results in a poor performance of the fuel cell stack.
Accordingly, the excess nitrogen must be bled from the system. The
bleed valve may also be used to remove the excess nitrogen. Ice may
prevent the operation of the bleed valve used to remove the
nitrogen from the fuel cell stack, preventing optimal operation of
the fuel cell stack.
The cathode exhaust gas may be used to humidify oxygen or air
entering the cathode using a water vapor transfer unit (WVT).
Liquid water present in the cathode exhaust gas indicates the
cathode is over humidified. When the WVT is exposed to liquid
water, water in excess of the desired amount may be reintroduced
into the cathode. To purge water from the cathode, a bypass valve
may be used to direct the cathode exhaust gas away from the WVT. A
bypass valve system is typically bulky and generally includes an
actuator and a sensor.
Atmospheric air may be compressed and cooled before entering the
WVT and cathode. Humidified air leaving the WVT during a cold start
may condense and accumulate prior to entering the cathode. It is
desirable to remove the condensate prior to the air entering the
cathode. Removal of the condensate minimizes the startup time of
the fuel cell stack in cold weather. The condensate is typically
drained using an intermittently operated draining system. The
draining system may take up considerable space and include a
collection point, a drain valve, and a condensate level sensor.
It would be desirable to produce a passive water drain for a fuel
cell stack that minimizes a complexity of an anode reactant
recycler, eliminates the need for bypass valve systems used to
remove water from the cathode exhaust, and eliminates the need for
condensate draining systems used for compressed air entering the
cathode.
SUMMARY OF THE INVENTION
Presently provided by the invention, a passive water drain for a
fuel cell stack that simplifies the anode reactant recycler,
eliminates the need for bypass valve systems used to remove water
from the cathode exhaust, and eliminates the need for condensate
draining systems used for compressed air entering the cathode, has
surprisingly been discovered.
In one embodiment, a device for receiving a fluid stream comprises
a main body having a cavity formed therein, the main body including
an inlet, an outlet, and a drain, the inlet adapted to receive the
fluid stream, an interior element disposed in the cavity of the
main body adapted to increase a tortuosity of the fluid stream, and
a hydrophilic porous media disposed adjacent the drain in fluid
communication with the cavity, the hydrophilic porous media
militating against transfer of the fluid stream through the drain,
wherein the fluid stream is exhausted from the cavity through the
outlet.
In another embodiment, the device for receiving a fluid stream in a
fuel cell system comprises a main body having a cavity formed
therein, the main body including an inlet, an outlet, and a drain,
the inlet adapted to receive the fluid stream, an interior element
disposed in the cavity of the main body adapted to increase a
tortuosity of the fluid stream, a hydrophilic porous media
sealingly disposed in the drain in fluid communication with the
cavity, and a liquid retention feature disposed adjacent the
hydrophilic porous media, wherein the hydrophilic porous media
militates against transfer of the fluid stream through the drain
and the fluid stream is exhausted from the cavity through the
outlet.
The invention also provides methods for separating a liquid from a
fluid stream.
In one embodiment, the method comprises steps of providing a device
having a main body with a cavity formed therein and including an
inlet, an outlet, and a drain, providing an interior element
disposed in the cavity, providing a hydrophilic porous media in
fluid communication with the cavity, one of a thickness and an area
of the hydrophilic porous media selected to militate against
transfer of the fluid stream through the drain, providing the fluid
stream including a liquid from a source of fluid to the inlet,
increasing a tortuosity of the fluid stream with the interior
element, thereby causing the liquid to collect in the cavity,
hydrating the hydrophilic porous media with the liquid collected in
the cavity, thereby militating against transfer of the fluid stream
through the drain, draining the liquid in excess of a saturation
point of the hydrophilic porous media through the drain, and
exhausting the fluid stream from the cavity through the outlet.
BRIEF DESCRIPTION OF THE DRAWINGS
The above, as well as other advantages of the present invention,
will become readily apparent to those skilled in the art from the
following detailed description, when considered in the light of the
accompanying drawings in which:
FIG. 1 illustrates a schematic flow diagram of an anode reactant
recycling system, a cathode reactant system, and a fuel cell stack
according to the present invention;
FIG. 2 illustrates a schematic flow diagram of the anode reactant
recycling system illustrated in FIG. 1;
FIG. 3 illustrates a schematic flow diagram of an anode reactant
recycling system according to another embodiment of the present
invention;
FIG. 4 illustrates a schematic flow diagram of an anode reactant
recycling system according to another embodiment of the present
invention;
FIG. 5 illustrates a schematic side cross sectional view of a
cathode inlet passive water drain for the embodiment illustrated in
FIG. 1; and
FIG. 6 illustrates a schematic side cross sectional view of a
cathode outlet passive water drain for the embodiment illustrated
in FIG. 1.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
The following detailed description and appended drawings describe
and illustrate various exemplary embodiments of the invention. The
description and drawings serve to enable one skilled in the art to
make and use the invention, and are not intended to limit the scope
of the invention in any manner. In respect of the methods
disclosed, the steps presented are exemplary in nature, and thus,
the order of the steps is not necessary or critical.
FIG. 1 illustrates a fuel cell system 10 according to an embodiment
of the present invention. The fuel cell system 10 includes an anode
reactant system 12, a fuel cell stack 14, and a cathode reactant
system 16.
The anode reactant system 12 includes a fuel source 18 and an anode
reactant recycler 20. The fuel source 18 is typically a storage
vessel used to store a fluid such as hydrogen under pressure, but
other fuel sources may be used. A fuel conduit 22 provides fluid
communication between the fuel source 18 and the fuel cell stack
14. In the embodiment shown, a fuel heater 24 is disposed in the
fuel conduit 22 between the fuel source 18 and the anode reactant
recycler 20. The fuel heater 24 raises a temperature of the fuel
entering the anode reactant recycler 20.
The anode reactant recycler 20 includes an injector 26, an ejector
28, a water separator 30, and a passive water drain 32. The anode
reactant recycler 20 recycles unused fuel leaving the fuel cell
stack 14, removes condensate that collects within the anode
reactant recycler 20, and bleeds contaminants such as nitrogen from
the anode reactant system 12. The injector 26 and the ejector 28
are in fluid communication with an anode inlet 34 of the fuel cell
stack 14. An anode outlet 36 of the fuel cell stack 14 is in fluid
communication with the anode reactant recycler 20. A bleed conduit
38 having a bleed valve 40 disposed therein provides fluid
communication between the anode reactant recycler 20 and an exhaust
42 of the fuel cell system 10. Alternately, the bleed conduit 38
may be directed to the cathode reactant system 16 to heat the
cathode during a cold start of the fuel cell stack 14. A drain
conduit 44 is in fluid communication with the passive water drain
32 and the exhaust 42.
The cathode reactant system 16 includes an oxidant source 46, a
compressor 48, an intercooler 50, a water vapor transfer unit (WVT)
52, a cathode inlet passive water drain 54, and a cathode outlet
passive water drain 56. The oxidant source 46 is typically
atmospheric air, but other oxidant sources may be used. An oxidant
conduit 58 provides fluid communication between the oxidant source
46 and the fuel cell stack 14. In certain embodiments, the
intercooler 50 can be eliminated from the cathode reactant system
16. The intercooler 50 raises or lowers a temperature of the
oxidant before the oxidant enters one of a cathode inlet 60 of the
fuel cell stack 14 and the WVT 52. The temperature of the oxidant
is typically raised or lowered to a temperature of a coolant used
in the fuel cell stack 14. The cathode inlet passive water drain 54
is disposed in the oxidant conduit 58 downstream from the WVT 52 to
remove condensate therefrom. A drain conduit 61 is in fluid
communication with the exhaust 42 for the removal of condensate
from the cathode inlet passive water drain 54. The WVT 52
humidifies the oxidant before the oxidant enters the cathode inlet
passive water drain 54. Exhaust fluids (such as unused oxidant and
water vapor) exit the fuel cell stack 14 through a cathode outlet
62 and enter the cathode outlet passive water drain 56. After
condensate is removed from the exhaust fluids with the cathode
outlet passive water drain 56, the exhaust fluids enter the WVT 52.
A drain conduit 64 is in fluid communication with the exhaust 42
for the removal of condensate from the cathode outlet passive water
drain 56. The WVT 52 includes a vapor permeable membrane separating
the oxidant conduit 58 from an exhaust conduit 66, permitting the
exhaust fluids to humidify the oxidant entering the cathode inlet
60.
FIG. 2 illustrates the anode reactant recycler 20 according to an
embodiment of the invention. The anode reactant recycler 20 shown
includes the fuel heater 24. The anode reactant recycler 20 has a
cavity 80 formed therein. The cavity 80 and the ejector 28 are in
fluid communication with the anode inlet 34 of the fuel cell stack
14. The anode outlet 36 is in fluid communication with a recycler
inlet 82. An upstream strainer 83 may be placed in the recycler
inlet 82 or other serviceable upstream location to prevent
particulate matter from entering the passive water drain 32.
Particulate matter entering the anode reactant recycler 20 may clog
the passive water drain 32, militating against removal of water
from the anode reactant recycler 20. The upstream strainer 83 may
be coupled to the recycler inlet 82 by any conventional means such
as adhesion or a friction fit, for example. Any conventional
non-corrosive material including pores formed therein such as a
glass fiber mat, a sintered metal, a bonded metal mesh, a woven
cloth, and a porous foam, for example, may be used to form the
upstream strainer 83. The pores formed in the upstream strainer 83
are sized to remove particulate matter that may clog or impair
performance of the passive water drain 32. The bleed conduit 38 and
the drain conduit 44 are in fluid communication with the exhaust
42. Alternately, the bleed conduit 38 may be directed to the
cathode reactant system 16 to heat the cathode during a cold start
of the fuel cell stack 14. The anode reactant recycler 20 may be
formed from any conventional material such as a metal, a metal
alloy, a plastic, and a plastic composite, for example. The anode
reactant recycler 20 may be formed separately or integrally formed
with a fuel cell end unit of the fuel cell stack 14. As shown, the
anode reactant recycler 20 includes the injector 26, the ejector
28, the water separator 30, and the passive water drain 32.
The injector 26 is a fuel injector as is known in the art, wherein
the injector 26 provides fluid communication between the fuel
source 18 and the ejector 28. The fuel from the fuel source 18 is
delivered by the injector 26 to an inlet of the ejector 28.
The ejector 28 is disposed between the injector 26 and the anode
inlet 34, and includes a Venturi passage 84. The Venturi passage 84
includes a neck portion having a diameter smaller than a diameter
of a remaining passage portions. Any conventional material such as
a metal, a metal alloy, a plastic, and a plastic composite, for
example, may be used to form the ejector 28. The ejector 28 may be
integrally formed as a portion of the fuel cell end unit or the
anode reactant recycler 20. Any conventional means such as
fastening or adhesion, for example, may be used to couple the
ejector 28 to at least a portion of the anode reactant recycler 20
when the ejector 28 is formed separately. As is known in the art,
combining the injector 26 and the ejector 28 in series forms a jet
pump or an aspirator.
As shown, the water separator 30 is disposed in the cavity 80 of
the anode reactant recycler 20 between the recycler inlet 82 and
the ejector 28. The water separator 30 may be integrally formed
with the anode reactant recycler 20. Alternately, the water
separator 30 may be formed separately from and coupled to the anode
reactant recycler 20 by any conventional means such as fastening or
adhesion, for example. Any conventional material such as a metal, a
metal alloy, a plastic, and a plastic composite, for example, may
be used to form the water separator 30. The water separator 30
includes a plurality of interior elements 86. As illustrated in
FIGS. 2, 3, and 4, the water separator 30 includes a plurality of
spaced apart and substantially parallel baffles. Other baffle
arrangements, a series of chambers, a plurality of boustrophedonic
passages, a cyclonic separator, or any other type of interior
element may also be included with the water separator 30.
The passive water drain 32 includes a hydrophilic porous media 88
and a liquid retention feature 90. The hydrophilic porous media 88
is sealingly disposed in the drain conduit 44 of the anode reactant
recycler 20. The cavity 80, the drain conduit 44, and the water
separator 30 are in fluid communication with the media 88. The
media 88 may be coupled to the anode reactant recycler 20 by any
conventional means such as adhesion or a friction fit, for example.
Any conventional non-corrosive material including pores formed
therein such as a glass fiber mat, a sintered metal, a bonded metal
mesh, a woven cloth, and a porous foam, for example, may be used to
form the hydrophilic porous media 88. The pores formed in the
hydrophilic porous media 88 are typically from about 1 micron to
about 10 microns in diameter. A material forming the hydrophilic
porous media 88 may be selected based on a nominal pore size and a
uniformity of the pores formed therein. As shown, the hydrophilic
porous media 88 is a single layer of material, but a plurality of
stratified layers of material having a nominally larger pore size
may be used.
The liquid retention feature 90 is disposed in the drain conduit 44
of the anode reactant recycler 20. The liquid retention feature 90
may be integrally formed with the anode reactant recycler 20.
Alternately, the liquid retention feature 90 may be formed
separately and coupled to the anode reactant recycler 20 by any
conventional means such as fastening or adhesion, for example. Any
conventional material such as a metal, a metal alloy, a plastic,
and a plastic composite, for example, may be used to form the
liquid retention feature 90. The liquid retention feature 90
collects and retains a desired amount of condensate exiting the
cavity 80 through the drain conduit 44. As shown in FIG. 2, the
liquid retention feature 90 has a substantially "L" shaped
cross-section and is shaped to substantially correspond to the
drain conduit 44, but any shape may be used.
The drain conduit 44 is disposed adjacent the anode reactant
recycler 20 and provides fluid communication between the cavity 80
and the exhaust 42. The drain conduit 44 may be integrally formed
as a portion of the fuel cell end unit or the anode reactant
recycler 20. Alternately, the drain conduit 44 may be separately
formed, and may be formed from any conventional material such as a
metal, a metal alloy, a plastic, and a plastic composite, for
example. Any conventional means such as fastening or adhesion, for
example, may be used to couple the drain conduit 44 to the anode
reactant recycler 20 when the drain conduit 44 is formed
separately. As shown, the drain conduit 44 is vertically oriented.
However, other orientations can be used.
The bleed conduit 38 is disposed adjacent the anode reactant
recycler 20 and provides fluid communication between the cavity 80
and the exhaust 42. Alternately, the bleed conduit 38 may be
directed to the cathode reactant system 16 to heat the cathode
during a cold start of the fuel cell stack 14. The bleed conduit 38
may be integrally formed as a portion of the fuel cell end unit or
the anode reactant recycler 20, and may be formed from any
conventional material such as a metal, a metal alloy, a plastic,
and a plastic composite, for example. Any conventional means such
as fastening or adhesion, for example, may be used to couple the
bleed conduit 38 to the anode reactant recycler 20 when the bleed
conduit 38 is formed separately. As shown, the bleed conduit 38
includes the bleed valve 40 disposed therein. A controller and an
actuator (not shown) in communication with the bleed valve 40
change a position of the bleed valve 40 as desired. The valve 40
may be positioned in an open position, a closed position, or an
intermediate position. The bleed valve 40 may be a solenoid
operated gate valve, but other valves types may be used.
FIG. 3 shows another embodiment of the invention similar to that
shown in FIG. 2. Reference numerals for similar structure in
respect of the description of FIG. 2 are repeated in FIG. 3 with a
prime (') symbol.
The anode reactant recycler 20' shown includes the fuel heater 24'.
The passive water drain 92 includes a hydrophilic porous media 94
and a liquid retention feature 96. The hydrophilic porous media 94
is sealingly disposed in the drain conduit 44' of the anode
reactant recycler 20'. The cavity 80', the drain conduit 44', and
the water separator 30' are in fluid communication with the media
94. The media 94 may be coupled to the anode reactant recycler 20'
by any conventional means such as adhesion or a friction fit, for
example. The liquid retention feature 96 is disposed in the drain
conduit 44' of the anode reactant recycler 20'. The liquid
retention feature 96 may be integrally formed with the anode
reactant recycler 20'. Alternately, the liquid retention feature 96
may be formed separately and coupled to the anode reactant recycler
20' by any conventional means such as fastening or adhesion, for
example. The liquid retention feature 96 militates against a
desired amount of condensate exiting the cavity 80' through the
drain conduit 44'. As shown in FIG. 3, the liquid retention feature
96' has a substantially rectangular shaped cross-section and
extends across a width of the drain conduit 44', but any shape may
be used.
The drain conduit 44' is disposed adjacent the anode reactant
recycler 20' and provides fluid communication between the cavity
80' and the exhaust (not shown). The drain conduit 44' may be
integrally formed as a portion of the fuel cell end unit or the
anode reactant recycler 20'. Alternately, the drain conduit 44' may
be separately formed, and may be formed from any conventional
material such as a metal, a metal alloy, a plastic, and a plastic
composite, for example. Any conventional means such as fastening or
adhesion, for example, may be used to couple the drain conduit 44'
to the anode reactant recycler 20' when the drain conduit 44' is
formed separately. As shown, the drain conduit 44' is substantially
horizontally oriented. However, other orientations can be used.
FIG. 4 shows another embodiment of the invention similar to that
shown in FIGS. 2 and 3. Reference numerals for similar structure in
respect of the description of FIGS. 2 and 3 are repeated in FIG. 4
with a double prime ('') symbol.
As shown, the anode reactant recycler 20'' does not include a fuel
heater. The cavity 80'' of the anode reactant recycler 20'' is in
fluid communication with the anode inlet 34'' of the fuel cell
stack (not shown). The anode outlet 36'' is in fluid communication
with an ejector 100 and the bleed conduit 38''. An upstream
strainer (not shown) may be placed in the anode outlet 36'' or
other serviceable upstream location to prevent particulate matter
from entering the passive water drain 92''. Particulate matter
entering the anode reactant recycler 20'' may clog the passive
water drain 92'', militating against removal of water from the
anode reactant recycler 20''. The bleed conduit 38'' and the drain
conduit 44'' are in fluid communication with the exhaust (not
shown). Alternately, the bleed conduit 38'' may be directed to the
cathode reactant system (not shown) to heat the cathode during a
cold start of the fuel cell stack.
The injector 26'' is a fuel injector as is known in the art,
wherein the injector 26'' provides fluid communication between the
fuel source (not shown) and the ejector 100. The injector 26'' is
disposed in the anode reactant recycler adjacent a recycler inlet
106. The fuel from the fuel source is delivered by the injector
26'' to an inlet of the ejector 100.
The ejector 100 is disposed between the injector 26'' and the
cavity 80'', and includes a Venturi passage 108. The ejector 100
may be integrally formed as a portion of the fuel cell end unit or
the anode reactant recycler 20''. Any conventional means such as
fastening or adhesion, for example, may be used to couple the
ejector 100 to at least a portion of the anode reactant recycler
20'' when the ejector 100 is formed separately. As is known in the
art, combining the injector 26'' and the ejector 100 in series
forms a jet pump or an aspirator.
The bleed conduit 38'' is disposed adjacent the anode outlet 36''
and provides fluid communication between the anode outlet 36'' and
the exhaust (not shown). Alternately, the bleed conduit 38'' may be
directed to the cathode reactant system to heat the cathode during
a cold start of the fuel cell stack. The bleed conduit 38'' may be
integrally formed as a portion of the fuel cell end unit or the
anode reactant recycler 20'', and may be formed from any
conventional material such as a metal, a metal alloy, a plastic,
and a plastic composite, for example. Any conventional means such
as fastening or adhesion, for example, may be used to couple the
bleed conduit 38'' to the anode reactant recycler 20'' when the
bleed conduit 38'' is formed separately. As shown, the bleed
conduit 38'' includes the bleed valve 40'' disposed therein. A
controller and an actuator (not shown) in communication with the
bleed valve 40'' change a position of the bleed valve 40'' as
desired. The valve 40'' may be positioned in an open position, a
closed position, or an intermediate position.
FIG. 5 shows another embodiment of the invention similar to that
shown in FIGS. 1, 2, and 3. Reference numerals for similar
structure in respect of the description of FIGS. 1, 2, and 3 are
repeated in FIG. 5 with a triple prime (''') symbol.
FIG. 5 illustrates the cathode inlet passive water drain 54'''. The
cathode inlet passive water drain 54''' is a structure having a
cavity 80''' formed therein. The cavity 80''' forms a portion of
the oxidant conduit 58'''. The oxidant conduit 58''' located
downstream from the cavity 80''' is in fluid communication with the
fuel cell stack (not shown). The oxidant conduit 58''' located
upstream from the cavity 80''' is typically in fluid communication
with the WVT. An upstream strainer (not shown) may be placed in the
oxidant conduit 58''' or other serviceable upstream location to
prevent particulate matter from entering the passive cathode inlet
passive water drain 54'''. Particulate matter entering the cathode
inlet passive water drain 54''' may clog the passive water drain
32''', militating against removal of water from the cathode inlet
passive water drain 54'''. In other embodiments of the invention
not shown, the oxidant conduit 58''' located upstream from the
cavity 80''' may be in fluid communication with the intercooler
(not shown) and the compressor (not shown). The drain conduit 61'''
is in fluid communication with the exhaust (not shown). The cathode
inlet passive water drain 54''' may be formed from any conventional
material such as a metal, a metal alloy, a plastic, and a plastic
composite, for example. The cathode inlet passive water drain 54'''
may be formed separately from other components or may be integrally
formed within a fuel cell end unit of the fuel cell stack. As
shown, the cathode inlet passive water drain 54''' includes an
interior element 110 and the passive water drain 32'''.
The interior element 110 is disposed in the cavity 80''' of the
cathode inlet passive water drain 54''' between an inlet and an
outlet thereof. The cathode inlet passive water drain 54''' may be
integrally formed with the interior element 110. Alternately, the
interior element 110 may be formed separately and coupled to the
cathode inlet passive water drain 54''' by any conventional means
such as fastening or adhesion, for example. Any conventional
material such as a metal, a metal alloy, a plastic, and a plastic
composite, for example, may be used to form the interior element
110. As shown, the interior element 110 is a rectangular shaped
baffle. Other shapes, a chamber, a boustrophedonic passage, a
cyclonic separator, or any other type of interior element may also
be included with the interior element 110.
The passive water drain 32''' includes a hydrophilic porous media
88''' and a liquid retention feature 90'''. The hydrophilic porous
media 88''' is sealingly disposed in the drain conduit 61''' of the
cathode inlet passive water drain 54'''. The cavity 80'', the drain
conduit 61''', and the interior element 110 are in fluid
communication with the media 88'''. The media 88''' may be coupled
to the cathode inlet passive water drain 54''' by any conventional
means such as adhesion or a friction fit, for example.
The liquid retention feature 90''' is disposed in the drain conduit
61''' of the cathode inlet passive water drain 54'''. The liquid
retention feature 90''' may be integrally formed with the cathode
inlet passive water drain 54'''. Alternately, the liquid retention
feature 90''' may be formed separately and coupled to the cathode
inlet passive water drain 54''' by any conventional means such as
fastening or adhesion, for example. The liquid retention feature
90''' collects and retains a desired amount of condensate exiting
the cavity 80''' through the drain conduit 61'''. As shown in FIG.
5, the liquid retention feature 90''' has a substantially "L"
shaped cross-section and is shaped to substantially correspond to
the drain conduit 61''', but any shape may be used.
FIG. 6 shows another embodiment of the invention similar to that
shown in FIGS. 1, 2, 3, and 5. Reference numerals for similar
structure in respect of the description of FIGS. 1, 2, 3, and 5 are
repeated in FIG. 6 with a quadruple prime ('''') symbol.
FIG. 6 illustrates the cathode outlet passive water drain 56''''.
The cathode outlet passive water drain 56'''' includes a cavity
80'''' formed therein. The cavity 80'''' forms a portion of the
exhaust conduit (not shown). The exhaust conduit located downstream
from the cavity 80'''' is in fluid communication with the WVT
52''''. The exhaust conduit located upstream from the cavity 80''''
is in fluid communication with the cathode outlet 62''''. An
upstream strainer (not shown) may be placed in the cathode outlet
62'''' or other serviceable upstream location to prevent
particulate matter from entering the cathode outlet passive water
drain 56''''. Particulate matter entering the cathode outlet
passive water drain 56'''' may clog the passive water drain 92'''',
militating against removal of water from the cathode outlet passive
water drain 56''''. The drain conduit 64'''' is in fluid
communication with the exhaust (not shown). The cathode outlet
passive water drain 56'''' may be formed from any conventional
material such as a metal, a metal alloy, a plastic, and a plastic
composite, for example. The cathode outlet passive water drain
56'''' may be formed separately from other components or may be
integrally formed within a fuel cell end unit of the fuel cell
stack (not shown). As shown, the cathode outlet passive water drain
56'''' includes an interior element 110'''' and the passive water
drain 92''''.
The interior element 110'''' is disposed in the cavity 80'''' of
the cathode outlet passive water drain 56'''' between an inlet and
an outlet thereof. The cathode outlet passive water drain 56''''
may include the interior element 110'''' as integrally formed.
Alternately, the interior element 110'''' may be formed separately
and coupled to the cathode outlet passive water drain 56'''' by any
conventional means such as fastening or adhesion, for example. Any
conventional material such as a metal, a metal alloy, a plastic,
and a plastic composite, for example, may be used to form the
interior element 110''''. As shown, the interior element 110'''' is
a rectangular shaped baffle. Other shapes, a chamber, a
boustrophedonic passage, a cyclonic separator, or any other type of
interior element may also be used as the interior element
110''''.
The passive water drain 92'''' includes a hydrophilic porous media
94'''' and a liquid retention feature 96''''. The hydrophilic
porous media 94'''' is sealingly disposed in the drain conduit
64'''' of the cathode outlet passive water drain 56''''. The cavity
80'''', the drain conduit 64'''', and the interior element 110''''
are in fluid communication with the media 94''''. The media 94''''
may be coupled to the cathode outlet passive water drain 56'''' by
any conventional means such as adhesion or a friction fit, for
example. The liquid retention feature 96'''' is disposed in the
drain conduit 64'''' of the cathode outlet passive water drain
56''''. The liquid retention feature 96'''' may be integrally
formed with the cathode outlet passive water drain 56''''.
Alternately, the liquid retention feature 96'''' may be formed
separately and coupled to the cathode outlet passive water drain
56'''' by any conventional means such as fastening or adhesion, for
example. The liquid retention feature 96'''' militates against a
specified amount of condensate from exiting the cavity 80''''
through the drain conduit 64''''. As shown in FIG. 6, the liquid
retention feature 96'''' has a substantially rectangular shaped
cross-section and extends across a width of the drain conduit
64'''', but any shape may be used.
During operation of the fuel cell system 10, an anode exhaust
stream is exhausted from the fuel cell stack 14 through the anode
outlet 36, 36'. The anode exhaust stream contains unused fuel and
byproducts such as water and nitrogen. Upon the exhaust stream
entering the recycler inlet 82, 82' of the anode reactant recycler
20, 20', the exhaust stream flows across the water separator 30,
30'. As the exhaust stream flows across the water separator 30,
30', the interior elements 86, 86' or other water capture features
impede the exhaust stream. A resulting increased tortuosity of the
exhaust stream causes water present in the exhaust stream to
collect on the interior elements 86, 86', removing the water from
the exhaust stream. As the water collects on the water separator
30, 30', gravity causes the water to drain from the interior
elements 86, 86' and onto an interior surface of the anode reactant
recycler 20, 20'. As shown in FIG. 2, the interior surface guides
the water towards the passive water drain 32, hydrating the
hydrophilic porous media 88 and filling the liquid retention
feature 90 with water. As shown in FIG. 3, the interior surface
guides the water towards the passive water drain 92, hydrating the
hydrophilic porous media 94 and filling a portion of the drain
conduit 44' restrained by the liquid retention feature 96 with
water.
The exhaust stream continues through the cavity 80, 80' and enters
the jet pump (injector 26, 26' and ejector 28, 28'). The jet pump
facilitates an intake of the exhaust stream through the use of the
Venturi effect. Sufficient mixing of the fuel and the exhaust
stream is thus effected through the use of the injector 26, 26' and
the ejector 28, 28'. After injection of the fuel and mixing, the
exhaust stream is "recycled" and has a higher fuel content and a
lower water content and re-enters the fuel cell stack 14 through
the anode inlet 34, 34'.
The hydrophilic porous media 88, 94 militates against a transfer of
the exhaust stream through the media 88, 94 when hydrated by water.
A pressure the hydrophilic porous media 88, 94 can withstand may be
calculated by the bubble pressure method of surface tension. The
relationship of the bubble pressure of a medium having pores of a
specified diameter can be expressed as the following equation:
P.sub.bubble=4.sigma.*cos(.theta.)/D.sub.pore where, P.sub.bubble
is a maximum pressure the hydrophilic porous media 88, 94 can
withstand when hydrated; .sigma. is the surface tension of water;
.theta. is the contact angle of the hydrophilic porous media 88,
94; and D.sub.pore is the diameter of the pores in the hydrophilic
porous media 88, 94. As nonlimiting examples, the pores in the
hydrophilic porous media 88, 94 having the diameter of about 2
microns yield a bubble pressure of about 116 kPa, and the pores
having the diameter of about 5 microns yield a bubble pressure of
about 46 kPa, where the contact angle of the hydrophilic porous
media 88, 94 is about 30.degree. and the surface tension of water
is 0.067 N/m.
A thickness or the area of the hydrophilic porous media 88, 94 may
be selected to militate against excessive gas transfer to the drain
conduit 44, 44' in the event the hydrophilic porous media 88, 94
becomes dry. The hydrophilic porous media 88, 94 may become dry
after extended periods of operation at elevated temperatures or
when the oxidant has a low relative humidity. The relationship of
the flow rate through a medium having a specified permeability,
area, and thickness can be expressed as the following equation:
Q.sub.trans=kA.DELTA.P/.mu.L Where, Q.sub.trans is the volume flow
rate through the hydrophilic porous media 88, 94; k is the
permeability (a function of the pore size and the material
tortuosity) of the hydrophilic porous media 88, 94; A is the area
of the hydrophilic porous media 88, 94; .DELTA.P is the
differential pressure across the hydrophilic porous media 88, 94;
.mu. is the viscosity of the fluid passing through the hydrophilic
porous media 88, 94; and L is the thickness of the hydrophilic
porous media 88, 94. Accordingly, the thickness of the hydrophilic
porous media 88, 94 may be increased or the area of the hydrophilic
porous media 88, 94 exposed to the cavity 80, 80' may be decreased
to reduce gas transfer through the hydrophilic porous media 88, 94
when dry without affecting the bubble pressure of the hydrophilic
porous media 88, 94.
A saturation point for the hydrophilic porous media 88, 94 is the
condition where the hydrophilic porous media 88, 94 has absorbed
the greatest amount of water it can hold. The water in excess of
the media 88, 94 saturation point is restrained by the liquid
retention feature 90, 96 until the water overflows the liquid
retention feature 90, 96 and exits the anode reactant recycler 20,
20' through the drain conduit 44, 44'.
After periods of non-operation of the fuel cell system 10, nitrogen
or other gases diffuse into the anode reactant system 12 and may be
purged therefrom to facilitate starting of the fuel cell system 10.
During purging, the bleed valve 40, 40' is opened, allowing the
exhaust stream to be exhausted through the bleed conduit 38, 38' by
operating the injector 26, 26', removing the nitrogen or other
gases present in the anode reactant system 12. Further, the anode
reactant system 12 may be purged intermittently during operation of
the fuel cell system 10 to remove byproducts that may inhibit
performance of the fuel cell system 10. The exhaust stream having a
higher fuel content (due to fuel injection) and a lower water
content (after flowing across the water separator 30, 30') may
re-enter the fuel cell stack 14 through the anode inlet 34,
34'.
As shown in FIG. 4, an anode exhaust stream is exhausted from the
fuel cell stack (not shown) through the anode outlet 36''. The
anode exhaust stream contains unused fuel and byproducts such as
water and nitrogen. The exhaust stream enters the recycler inlet
106 of the anode reactant recycler 20'', and continues to the jet
pump (injector 26'' and ejector 100). The jet pump facilitates an
intake of the exhaust stream through the use of the Venturi effect.
Sufficient mixing of the fuel and the exhaust stream is thus
effected through the use of the injector 26'' and the ejector 100.
The fuel (being unheated) causes water vapor present in the exhaust
stream to condense. The exhaust stream then flows across the water
separator 30'', removing the water therefrom. The water is then
removed from the anode reactant recycler 20'' through the passive
water drain 92''. The exhaust stream having a higher fuel content
(due to fuel injection) and a lower water content (after flowing
across the water separator 30'') re-enters the fuel cell stack
through the anode inlet 34''.
A cathode inlet stream enters the fuel cell stack 14 through the
cathode inlet 60. When the oxidant source 46 is atmospheric air,
the cathode inlet stream contains water vapor. Further
humidification of the cathode inlet stream occurs when the cathode
inlet stream passes through the WVT 52. During cold starts, water
vapor present in the cathode inlet stream passing through the
compressor 48, the intercooler 50, and the WVT 52 is likely to
condense into water. As shown in FIG. 5, the cathode inlet stream
including water then enters the cavity 80'' of the cathode inlet
passive water drain 54''. As the cathode inlet stream flows across
the interior element 110, the cathode inlet stream is impeded. A
resulting increased tortuosity of the cathode inlet stream causes
water present in the cathode inlet stream to collect on the
interior element 110, removing the water from the cathode inlet
stream. As the water collects on the interior element 110 and the
interior surface of the cathode inlet passive water drain 54''',
gravity causes the water to drain from the interior element 110 and
the interior surface and onto the hydrophilic porous media 88'''.
The interior surface guides the water towards the passive water
drain 32''', hydrating the hydrophilic porous media 88''' and
filling the liquid retention feature 90''' with water. Water in
excess of the saturation point of the hydrophilic porous media
88''' exits the cathode inlet passive water drain 54''' through the
drain conduit 61'''. The cathode inlet stream having a reduced
amount of water continues through the cavity 80''' and exits the
cathode inlet passive water drain 54''', continuing through the
oxidant conduit 58''' to the fuel cell stack 14.
During operation of the fuel cell system 10, a cathode outlet
stream exits the fuel cell stack 14 through the cathode outlet 62,
62''''. Water generated within the fuel cell stack 14 is exhausted
through the cathode outlet 62, 62'''' in the cathode outlet stream.
As shown in FIG. 6, the cathode outlet stream including water then
enters the cavity 80'''' of the cathode outlet passive water drain
56''''. As the cathode outlet stream flows across the interior
element 110'''', the cathode outlet stream is impeded. A resulting
increased tortuosity of the cathode outlet stream causes water
present in the cathode outlet stream to collect on the interior
element 110'''', removing the water from the cathode outlet stream.
As the water collects on the interior element 110'''' and the
interior surface of the cathode outlet passive water drain 56'''',
gravity causes the water to drain from the interior element
110''''. The interior surface guides the water towards the passive
water drain 92'''', hydrating the hydrophilic porous media 94''''.
Water in excess of the saturation point of the hydrophilic porous
media 94'''' is retained by the liquid retention feature 96''''.
Water in excess of the amount the liquid retention feature 96''''
can retain exits the cathode reactant system 16 through the drain
conduit 64, 64''''. The cathode outlet stream having a reduced
amount of water continues through the cavity 80'''' and exits the
cathode outlet passive water drain 56''', continuing to the WVT 52,
52''''.
It should be appreciated that the passive water drain 32, 32''',
92, 92'', 92'''' eliminates the need for valves located in the
drain conduit 44, 44', 44'', 61''', 64''''. Further, it should be
appreciated that the passive water drain 92'''' eliminates the need
for bulky and costly valve systems that direct the cathode outlet
stream to bypass the WVT 52''''. The passive water drain 32''' also
eliminates the need for condensate draining systems used to remove
water from compressed air in the cathode inlet stream. The passive
water drain 32, 32''', 92, 92'', 92'''' in accord with the present
invention simplifies water removal from the anode reactant system
12, the fuel cell stack 14, and the cathode reactant system 16 by
requiring fewer components.
From the foregoing description, one ordinarily skilled in the art
can easily ascertain the essential characteristics of this
invention and, without departing from the spirit and scope thereof,
can make various changes and modifications to the invention to
adapt it to various usages and conditions.
* * * * *